The University of Colorado Boulder placed its main campus under a shelter-in-place order Monday afternoon after a report of shots fired at Norlin Library. The alert, issued just before 5 p.m. local time, prompted an evacuation of the library and nearby Sewall Hall while heavily armed officers swept the area. By 5:40 p.m., the University of Colorado Boulder Police Department said no evidence of gunfire, injuries or a shooter had been found and lifted the lockdown for all buildings except the library, which remained closed while investigators treated the call as a potential swatting incident—an intentional false report meant to provoke an armed police response. The scare is the latest in a string of shooting hoaxes at U.S. universities. Similar false reports have disrupted campuses at the University of Arkansas, Iowa State, Kansas State, the University of South Carolina, the University of Tennessee at Chattanooga and Villanova University in the past week, prompting renewed calls for federal authorities to identify the source of the coordinated swatting wave.